text: Ketones (and aldehydes) absorb strongly in the infra-red spectrum near 1750 cm, which is assigned to ν ("carbonyl stretching frequency"). The energy of the peak is lower for aryl and unsaturated ketones.
  Whereas H NMR spectroscopy is generally not useful for establishing the presence of a ketone, C NMR spectra exhibit signals somewhat downfield of 200 ppm depending on structure. Such signals are typically weak due to the absence of nuclear Overhauser effects. Since aldehydes resonate at similar chemical shifts, multiple resonance experiments are employed to definitively distinguish aldehydes and ketones.